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A combination switch including a time slot switch and a router for
receiving circuit-switched and Internet Protocol packet data.
A routing-switching base station in electronic communication with a
telecommunications network includes a combination time slot switch and
Internet Protocol switch, along with a plurality of transceivers.
Circuit-switched data and Internet Protocol packet data received from the
network and is passed on to the transceivers. The combination switch may
include a time slot switch and a router.
A routing radio base station includes a router in electronic communication
with a plurality of transceivers.

1. A combination switch in electronic communication with a
telecommunications network, wherein the telecommunications network
includes at least one frame of circuit-switched data and at least one
packet of Internet Protocol data, comprising: a time slot switch for
receiving the at least one frame of circuit-switched data; and a router
for receiving the at least one packet of Internet Protocol data in
electronic communication with the time slot switch.

2. The combination switch of claim 1, further comprising: at least one
central processing unit in electronic communication with the time slot
switch and the router.

4. The combination switch of claim 2, wherein the time slot switch is
implemented using at least one first digital signal processor in
electronic communication with the at least one central processing unit.

5. The combination switch of claim 4, wherein the router is implemented
using at least one second digital signal processor in electronic
communication with the at least one central processing unit.

6. A routing-switching base station in electronic communication with a
telecommunications network, wherein the telecommunications network
includes at least one frame of circuit-switched data and at least one
packet of Internet Protocol data, comprising: a combination time slot
switch and Internet Protocol switch for receiving the at least one frame
of circuit-switched data and the at least one packet of Internet Protocol
data; and a plurality of transceivers, wherein each one of the plurality
of transceivers is in electronic communication with the combination time
slot switch and Internet Protocol switch.

7. The routing-switching base station of claim 6, wherein at least one of
the plurality of transceivers receives a selected portion of the at least
one frame of circuit-switched data from the combination time slot switch
and Internet Protocol switch.

8. The routing-switching base station of claim 6, wherein at least one of
the plurality of transceivers receives at least one packet of Intern et
Protocol data from the combination time slot switch and Internet Protocol
switch.

9. The routing-switching base station of claim 6, further comprising: at
least one central processing unit in electronic communication with the
combination time slot switch and Internet Protocol switch.

10. The routing-switching base station of claim 9, wherein the at least
one central processing unit executes a network management protocol.

11. The combination switch of claim 9, wherein the combination time slot
switch and Internet Protocol switch is implemented using at least one
digital signal processor in electronic communication with the at least
one central processing unit.

12. The routing-switching base station of claim 6, wherein at least one of
the plurality of transceivers is a radio frequency transceiver.

13. A routing-switching base station in electronic communication with a
telecommunications network, wherein the telecommunications network
includes at least one frame of circuit-switched data and at least one
packet of Internet Protocol data, comprising: a time slot switch for
receiving the at least one frame of circuit-switched data; a router in
electronic communication with the time slot switch for receiving the at
least one packet of Internet Protocol data; and a plurality of
transceivers, wherein at least one of the plurality of transceivers is in
electronic communication with the time slot switch, and wherein at least
one of the plurality of transceivers is in electronic communication with
the Internet Protocol switch.

14. The routing-switching base station of claim 13, wherein the at least
one of the plurality of transceivers in electronic communication with the
time slot switch receives a selected portion of the at least one frame of
circuit-switched data.

15. The routing-switching base station of claim 13, wherein at least one
of the plurality of transceivers in electronic communication with the
router receives at least one packet of Internet Protocol data.

16. The routing-switching base station of claim 13, further comprising: at
least one central processing unit in electronic communication with the
time slot switch and the router.

17. The routing-switching base station of claim 16, wherein the at least
one central processing unit executes a network management protocol.

18. The routing-switching base station of claim 13, wherein the time slot
switch and the router are implemented using at least one digital signal
processor in electronic communication with the at least one central
processing unit.

19. The routing-switching base station of claim 13, wherein at least one
of the plurality of transceivers is a radio frequency transceiver.

20. A routing radio base station in electronic communication with a
telecommunications network, wherein the telecommunication network
includes at least one packet of Internet Protocol data, comprising: a
router for receiving the at least one packet of Internet Protocol data;
and a plurality of transceivers, wherein each one of the plurality of
transceivers is in electronic communication with the router.

21. The routing radio base station of claim 20, wherein at least one of
the plurality of transceivers receives at least one packet of Internet
Protocol data from the router.

22. The routing radio base station of claim 20, wherein the at least one
central processing unit executes a network management protocol.

23. The routing radio base station of claim 20, wherein the router is
implemented using at least one digital signal processor in electronic
communication with the at least one central processing unit.

Description

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from copending U.S.
Provisional Application for Pat. No. 60/177,805 titled "IP Packet Router
Integrated into a Radio Base Station" filed on Jan. 25, 2000, is related
thereto, is commonly assigned therewith, and the subject matter thereof
is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field of the Invention

[0003] The present invention relates in general to the telecommunications
field and, in particular, to an apparatus providing both circuit-switched
and packet-switched communications within a telecommunications network.

[0004] 2. Description of Related Art

[0005] Radio base stations (RBSs) within a mobile telephony system are
often used as network traffic transmission transfer points to other base
stations. Commonly used network topologies for connecting such base
stations to each other include the chain, ring, and tree topologies. A
single transmission link typically operates at rates of 2, 4, or 8
Mbit/second, which is greater than what is used by a single base station.
Therefore, multiple base stations often use a single transmission link.
Since the physical transmission medium is usually a radio link, base
station sites often house radio link equipment as well.

[0006] Each base station is typically connected to the transmission
network with one or more physical transmission links. The number of links
depends on the desired network topology, requirements for redundancy, and
the need for transmission capacity at the base station. In a
circuit-switched network 9, an internal switch matrix is used to
distribute fractions of connected bandwidth transmissions within the base
station to various transceivers and other signaling devices. The built-in
switch matrix is sometimes also used for switching excess bandwidth to
another link in the transmission network. This link is then used for
connection to other base stations. As shown in the prior art network
block diagram of FIG. 1A, a string of cascaded Internet nodes 20 and
radio base stations 30 are connected via network ports 32 within a
network 10, such as a combination Internet Protocol (IP) network 8 and a
switching network 9. In the network 10 topology shown in FIG. 1,
circuit-switched (STM) RBSs 30 are connected to Internet nodes 20. This
type of mixed network 10 is a common migration scenario as users migrate
from a completely circuit-switched network to an IP network. However, the
flexibility provided by packet switched connections and the IP Suite in
combination with circuit-switched networks requires a change in switching
technology. A converter 80 may be needed to convert signals between the
circuit-switched network 9 and the IP network 8.

[0007] Each RBS 30 is typically controlled by a Base Station Controller
(BSC) 40, and is connected to the controller 40 using a control/traffic
port 31. For example, the BSC 40 keeps track of resources within the STM
RBS 30. Such resources include the number and type of radio transceivers,
and the number and type of internal switching connections. The
connections within the switch 50 are known as "circuit-switched
connections." The switch 50 setup (i.e., how time slots within a time
frame 72 are switched) is accomplished using the BSC 40. Thus, it is the
job of the BSC 40 to track resources within the base station, which
include transceivers 60, 61 and connections within the switch 50. Once
the connections within the switch 50 are set, they are usually not
changed unless there is a disturbance within the transmission network 10
or the STM RBS 30 is shut down. The BSC 40 is also the source/destination
for connections to from the RBS 30.

[0008] The transmission interface, such as a 2 Mbit/sec G.703 interface,
delivers data in 32 byte frames 72, typically divided into one byte time
slots 74. The switch 50 switches all time slots that have the same
position in the frame 72 to one internal destination. For example,
considering the circuit-switched transceivers 60, 61, the switch 50 may
elect to send time slots #4 and #5, 76, 78, in each frame 72 to the
transceiver 61 via internal interface connection 70.

[0009] The typical messages which are used to load IP networks include
e-mail, file transfer, and accesses to the world-wide web. The length of
these messages, which are divided into packets 82, is often a few hundred
bytes, on up to a thousand or more bytes. For mobile radio systems, on
the other hand, speech packets are typically used to load the network.
These packets are quite small (i.e., on the order of 40-60 bytes) but are
transmitted rapidly (i.e., about every 20 milliseconds. This disparity in
packet size and frequency of transmission influences the optimal design
and routing elements within a mixed network 10.

[0010] IP packets 82 from the nodes 20 can only be inserted into available
time slots within the frames 72, which may require the use of a converter
80. Thus, IP-formatted information (i.e., packets 82) can be sent to the
BSC 40 without changing the operational characteristics of the switch 50.
In this way, IP-formatted data can be switched without routing, which is
inefficient.

[0011] As mentioned previously, the current solution is to divide the
available bandwidth into small selected portions (i.e., one or more time
slots) and assign them to each base station. However, when packet
transmissions are used within the mixed network 10, it is inefficient to
divide the link bandwidth into fractions (i.e., one or more consecutive
time slots) reserved to different base stations 30. The bandwidth for
each device or base station is thus reserved, and cannot be reused by
other devices. Thus, the transfer time for individual packets will be
fairly long if only a few time slots are used.

[0012] Thus, in mixed networks 10, there is a need for efficient data
distribution between RBSs 30 and the BSC 40. This need is independent of
the transmission network used. For migration from a circuit-switched
network 9 to an IP network 8, it should also be possible to mix IP
routing and STM switching.

[0013] A related problem is illustrated in prior art FIG. 1B. Sending
packet data 82 in an all-IP network 12 using conventional RBSs 30
requires an additional router 65, which adds cost and requires space.
Thus, a solution which obviates the need for the router 65 to communicate
packet data to RBSs 30 in an all-IP network 12 is also needed.

SUMMARY OF THE INVENTION

[0014] In accord with one embodiment of the present invention, a
combination switch includes a time slot switch and a router. The
combination switch is in electronic communication with the
telecommunications network providing frames of circuit-switched data and
packets of IP data, such that the time slot switch receives the
circuit-switched data, and the router receives the IP data. The router is
in electronic communication with the time slot switch.

[0015] The combination switch may include one or more central processing
units and one or more digital signal processors. Typically, the central
processing unit communicates with the time slot switch and the router
while executing one or more network management protocols, such as the
Simple Network Management Protocol (SNMP). Typically, a digital signal
processor is used to implement the time slot switch, and another digital
signal processor is used to implement the router.

[0016] In another embodiment, the invention includes a routing-switching
base station, which may be a radio base station, having a combination
time slot switch and Internet Protocol switch (or separate time slot
switch and router elements), in electronic communication with a plurality
of transceivers. The base station is in electronic communication with a
telecommunications network providing frames of circuit-switched data and
packets of IP data. The combination switch receives the data, and sends
it on to the plurality of transceivers.

[0017] In an alternative embodiment, a routing radio base station of the
present invention includes a router for receiving one or more packets of
IP data from the network, along with a plurality of transceivers which
are in electronic communication with the router. As the combination
routing-switching base station migration solution is incorporated into
networks over time, the need for the router and time slot switch
combination is expected to give way to the router radio base station
incorporating only the router.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete understanding of the method and apparatus of the
present invention may be had by reference to the following detailed
description when taken in conjunction with the accompanying drawings
wherein:

[0020] FIGS. 2A and 2B are block diagrams of the routing-switching base
station and the routing radio base station, respectively, of the present
invention; and

[0021] FIG. 3 is a schematic block diagram of the combination switch of
the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0022] The preferred embodiment of the present invention and its
advantages are best understood by referring to FIGS. 1-3 of the drawings,
like numerals being used for like and corresponding parts of the various
drawings.

[0023] Turning now to FIG. 2A, the routing-switching base station 100 of
the present invention can be seen. Included within the base station 100,
which may be a radio base station, is a combination time slot switch and
Internet Protocol switch 110, which may comprise a time slot switch 130
and a router 140. Through a series of internal interface connections 70,
the combination switch 110 is placed into electronic communication with a
plurality of transceivers 60, 90. The transceivers may be radio frequency
transceivers, optical transceivers, or other transceivers which operate
using electromagnetic energy to communicate information. Thus, when a
network supplies frames 72 of circuit-switched data to the base station
100, they may be received by the combination switch 110, and selected
portions of the frames 72 can be sent on to the transceivers 60.
Similarly, when packets 82 are received from the network, the IP data
packets 82 can be sent on to the transceivers 90. The transceivers 60, 90
may be similar or identical. The numeric differentiation is (only) used
to show that either transceiver 60, 90 may be used to send/receive frames
72 or selected packets 82 of data.

[0024] The combination switch 110 (or the individual elements of a time
slot switch 130 and a router 140) located in the routing-switching base
station 100 is a network migration solution that lends itself to use in
mixed networks having a combination of legacy equipment that operates
only with circuit-switched data, and newer equipment that operates using
packet-switched data. However, as time goes on, and the use of antiquated
circuit-switched equipment disappears, the routing-switching base station
100, which may be a radio base station, will not require circuit
switching functionality. The resulting routing radio base station 100'
will include the router 140 and one or more transceivers 90 in electronic
communication with the router 140, but not a time slot switch 130. This
solution, shown in FIG. 2B, solves the problem shown in FIG. 1B, wherein
an extra router 65 is needed to interface conventional RBSs 30 to the
all-IP network 12. In the invention, the equivalent of router 65, i.e.,
router 140, is now included within the routing radio base station 100'.

[0025] Thus, a cost efficient solution is provided by the present
invention to replace the built-in switch matrix 50 of prior art base
stations 30. The new (replacement) combination switch 110 is capable of
acting as a packet router, as a circuit switch, or as a device which can
provide packet-switching and circuit-switching at the same time. The
integrated device (i.e., switch) 110 is able to terminate traffic bound
for the base station 100, to forward traffic bound for other base
stations, and to distribute traffic internally within the base station
100. The router 140 within the switch 110 is programmed to understand and
implement the IP Suite.

[0026] The switch 110 (or the router 140 alone) can be implemented using
various logical building elements, and is not meant to be limited by the
exemplary illustrations given herein. For example, as shown in FIG. 3,
the switch 110 can be implemented using a central processing unit 260 and
one or more digital signal processing units 200. Using such a combination
of logical building elements provides several advantages. Central
processing units have a flexible construction set and can address large
amounts of memory. Thus, such central processing units are suitable to
process programs that are not time critical, and require complex
instruction sets. These units are relatively inexpensive, and it is
possible to combine multiple central processing units in a cluster to
achieve higher data processing rates.

[0027] On the other hand, Digital Signal Processors (DSPs) typically have
a specialized instruction set, and access less memory than that which can
be accessed by a central processing unit. Thus, DSPs are suitable to
process programs that are time critical, and require relatively
unsophisticated program instructions. DSPs can also be clustered to
provide increased throughput.

[0028] The various elements of the combination switch 110 can be grouped
into integrated circuits, such as a first integrated circuit 250, a
second integrated circuit 260, and a third integrated circuit 270. Thus,
in the exemplary implementation of the combination switch 110 shown in
FIG. 3, the first integrated circuit 250 may contain three DSPs 200
communicating with two memories 210, an external interface 230, and an
internal interface 240 using a common internal bus 255. The bus 255 is
also connected to the central processing unit 220, located on the second
integrated circuit 260. The memory 210 within the third integrated
circuit 270 is also connected to the bus 255. Of course integrated
circuits 250, 260 and 270 can all be further integrated into a single
circuit (not shown).

[0029] In the combination switch 110 configuration shown in FIG. 3, the
circuitry within the second integrated circuit 260 (i.e., the central
processing unit 220) can communicate using Direct Memory Access (DMA)
with the DSPs 200 and the memories 210 located in the first integrated
circuit 250. Another bus (not shown in FIG. 3) may be used for DSP 200
instruction fetches from the memories 210, or other memories (not shown).
The integrated circuit 250 may also contain special hardware and/or
firmware for High-level Data Link Control (HDLC) protocol conversion. In
the exemplary configuration of FIG. 3, the time slot switch 130 may be
implemented using the interfaces 230, 240, the memories 210, and programs
in two of the three DSPs 200. The remaining DSP 200 (and excess capacity
of the other DSPs 200) and the central processing unit 220 and the DSPs
200 are used to execute the IP Instruction Suite. Some of the routines
needed for transferring a message through the combination switch 110, and
executed within the DSPs 200, might include HDLC controls, Point-to-Point
Protocol (PPP), Link Control Protocol/Neighbor Discovery Protocol
(LCP/NDP) for initiating PPP, multilink PPP, header compression, queuing
(e.g., quality of service) and policing algorithms, packet forwarding IP,
and the User Datagram Protocol (UDP). Typically, the memory 210 necessary
for storing programs executed in the DSPs 200, along with the memory 210
needed for a data storage, will be a few hundred kilobytes. The DSPs
should operate at a program execution speed of approximately one billion
instructions per second (i.e., 1,000 Mips).

[0030] In the central processing unit 220, several protocols are required
for setup, supervision, exception handling, etc. These include: IP
Options Part, IP fragmentation, Open Shortest Path First (OSPF) routing
protocol, and the Simple Network Management Protocol (SNMP). The memory
210 required by the central processing unit 220 should be on the order of
several megabytes. The operating speed of the central processing unit
will typically be about several million instructions per second (e.g.,
1-10 Mips).

[0031] The routing-switching base station 100, the routing radio base
station 100', and the combination switch 110 allow implementation of
inexpensive router functionality in the place of conventional radio base
stations, which contain only circuit-switching operational elements. Such
an implementation allows use of the combination switch as a general IP
packet router at little or no additional cost.

[0032] The combination switch 110 can be used as an internal packet switch
so that packets from different devices can share the entire bandwidth
allowed. Thus, the combination switch 110 can use a portion of the
bandwidth for the base station 100 for circuit switched data 72, and
another portion of the bandwidth for packet-switched data 82. Using an
internal router 140 for switching will provide faster packet transfer
speeds and shorter queuing delays for high priority packets when priority
mechanisms are used.

[0033] The combination switch 110 configuration also allows internal
devices, such as transceivers 60, 90, to be addressed as IP nodes, and if
desired, to be visible to the external network 10. Using a router 140 as
an internal switching device operating under the IP Suite means that
special, non-standard protocols, will not be needed to operate the switch
110.

[0034] Additional advantages of the switch 110 include automatic routing
updates when the surrounding network 10 is changed (e.g., using the OSPF
protocol); increased possibilities for plug-and-play base stations
connected to a routing-switching base station 100; standardized
supervision methods, operation, and maintenance (e.g., using the SNMP
protocol); and standardized methods for verifying quality of service,
policing, and resource allocation.

[0035] During migration operations, there will be the opportunity for
connecting routing-switching base stations where circuit-switch
connections are required. As noted above, in this case, circuit-switched
data can use some fraction of the bandwidth, while IP routed data can use
the remaining fraction of the bandwidth. Conversion routines from the IP
and circuit-switch formats can be implemented using the combination
switch 110 for direct interfacing to transceivers 60, 90. The
functionality of the switch 110, implemented as described above, can now
be changed using software so that the switch 110 can act as a time slot
switch 130 alone, a combination switch 130, or a router 140 alone, and
manual visits to the site of the switch 110 to change its function are
obviated. Also, as noted above, the routing radio base station 100' (see
FIG. 2B) may only require the presence of a router 140 and transceivers
90 when circuit-switched data is no longer present in the network 10.

[0036] Finally, the DSPs 200 can operate as high performance packet
switches, or as high performance circuit-switches. Circuit-switching and
packet-switching can also be accomplished simultaneously. The same DSP
200 can perform internal distribution of data to various transceivers 60,
90 and other signaling devices. The DSPs 200 can also be assigned
responsibility for internal data conversion (i.e., from circuit-switching
protocols to IP, and vice versa). The DSPs 200 can also handle data
routing and buffering, and administer Quality-of-Service functions within
the IP Suite. The router 140 can also be used to concentrate several
links that are lightly loaded into a single link for better utilization
of available bandwidth.

[0037] Although a preferred embodiment of the method and apparatus of the
present invention has been illustrated in the accompanying drawings and
described in the foregoing detailed description, it will be understood
that the invention is not limited to the embodiment disclosed, but is
capable of numerous rearrangements, modifications and substitutions
without departing from the scope of the invention as set forth and
defined by the following claims.